In a non stick pan, toast the pepitas on medium low heat for about three minutes, tossing and flipping the pepitas until they are slightly golden and fragrant. Remove from pan and set aside to cool.
Blistering/Roasting poblanos can be accomplished on stove top gas range, in oven or grill. A. Stove Top Gas Range: Blister poblanos on a medium open stove top flame turning as needed until all the skin is charred, about 10 minutes. B. In Oven: Heat oven to broiling. Set the poblanos on an unlined sheet pan and broil, turning the poblanos every 2-3 minutes to blister, for about 10 minutes. C. Grill: Heat grill to highest heat setting. Set poblanos on grill grate, turning the poblanos every 4-5 minutes to blister for about 10 minutes. Once blistered set the poblanos in a covered bowl for 10 minutes (this will make them easier to peel!). Peel, remove the stem and seeds and slice into bite size pieces. Set aside.
In a large saute pan, add 2 tsp of oil. Heat until shimmering. Turn heat to medium and add the zucchini. Cook, stirring only a few times, for about 8 minutes, a bit of browning is okay. Add the corn and cook for another 2 minutes (the pan will be a bit crowded). Remove from pan and set aside.
In the same pan, add the last 2 tsp of oil. Heat until shimmering. Turn heat to medium low and add the onions. Cook, stirring occasionally for about 8 minutes or until softened. Stir in garlic, cumin, sea salt and oregano. Stir to coat. Turn heat to low, add the poblanos, corn and zucchini mixture and the sour cream. Stir to incorporate all the ingredients on low heat to gently warm. A few more tablespoons of sour cream can be added if desired. Squeeze 1/2 lime over mixture, stir, remove from heat. Put a lid on it to keep warm.
Warm tortillas over a low open stove flame, about 20 seconds each side for charring or according to package directions. Serve warm tortillas with filling and toppings as desired.
To freeze, place zucchini mixture in a freezer proof container for up to three weeks. Thaw in the refrigerator overnight and gently rewarm over low heat.